Experiment of RF-knock out extraction for high precision range measurement

Carbon ion that is accelerated by synchrotron is treated in Gunma University Heavy Ion Medical Center (GHMC). We use broad beam irradiation system at present, and slow extraction system by RF(Radio Frequency) acceleration is adopted for extraction method. However, GHMC considers starting scanning irradiation now. In addition, we want to use carbon beam by RF-knock out extraction for precision range measurement. Therefore, RF-knock out extraction system is needed to restrain range struggling and beam position drifting. Range struggling of RF-knock out beam is one tenth of that of RF acceleration and also lateral beam position drifting is small. For that reason, RF-knock out irradiation system is useful for scanning beam and our precision range measurement. GHMC has OPF (Operation File) of 140, 290, and 400 MeV/n by RF-knock out extraction method at present. However, we intend to use 170 MeV/n carbon beam by RF-knock out because we need to measure the range of carbon beam precisely by reducing beam energy and energy struggling. Therefore, we made OPF of 170 MeV/n carbon beam by RF-knock out extraction, and carried out the extraction experience. Furthermore, using 290 MeV/n carbon beam, we compared RF-knock out with RF acceleration. We analyzed these data to determine whether 170 MeV/n carbon beam can be used for precision range measurement and radiation therapy or not. (author)